Jury deliberations on whether to execute Boston Marathon bomber Dzhokhar Tsarnaev or sentence him to life in prison without parole could begin Wednesday. The use of life without parole sentences in the US is growing rapidly.

Boston — Ken Hartman is 55 and healthy, but he says he feels like he was killed decades ago. When he was 19, he beat a homeless man to death in an alcohol- and drug-fueled rage, and he has spent the past 35 years in prison. So long as he is alive, he will not be eligible to leave.

Mr. Hartman is among the 50,000 prisoners in the United States serving life without parole sentences, a number that has increased 22 percent since 2008, according to a 2013 report by the Sentencing Project. And on Wednesday, the jury in the Boston Marathon bombings trial will begin deliberating over whether to add Dzhokhar Tsarnaev to that group.

In his case, life without parole is seen as the more humane option. The other alternative is death, and there is some evidence that, as states turn more to life without parole, it is partly from a humane desire to move away from the ultimate punishment. The number of people sentenced to death in the US has declined from 3,600 to 3,000 since 2000, according to the Death Penalty Information Center.

Yet the rapid expansion of life without parole also speaks to the array of laws, spawned by the get-tough-on-crime 1980s, that remain on the books and mandate such sentences. At least 3,000 people sentenced to life without parole were convicted of nonviolent offenses, a report by the American Civil Liberties Union found.

Cracks in that mind-set are beginning to appear, as states, Congress, and the Obama administration reconsider mandatory minimum sentencing laws. Polls show growing support for reforming such laws. But most experts agree that so long as the death penalty exists, life without parole will continue to exist in its wake – a humane alternative of debatable humaneness.

“The death penalty operates to basically overshadow life in prison without parole,” says Marion Vannier, a criminologist at the University of Oxford in Britain researching a doctoral dissertation on life without parole in the US.

The quadrupling of life without parole

When Hartman was sentenced in 1980, life without parole was a relatively new sentence in California, where he is serving his time in prison. It had been introduced after the US Supreme Court banned the death penalty in 1972. (It was reinstated in 1976.) California, along with several other states, added life without parole as a fallback punishment for the worst criminals.

Hartman was considered to be among that group because he was judged to have attempted to rob the victim as well. When he was sentenced, Hartman says, “It didn’t seem real.”

“At the time, I don’t think people saw life without possibility of parole as life without possibility of parole,” says Hartman in a phone interview with the Monitor from California State Prison-Los Angeles County prison in Lancaster.

Life without parole prisoners call it "death in slow motion" or "the other death penalty," and Hartman has started an advocacy group named the Other Death Penalty Project to raise awareness about life without parole sentences.

Since Hartman was sentenced, life without parole has gone from being an extremely rare sentence to being a far more common one. Mandatory minimum sentences for “habitual offenders” as well as the harsh sentencing included in the war on drugs have contributed to a quadrupling of the number of prisoners who received life without parole sentences between 1992 and 2012, according to the Sentencing Project report.

While most are in prison for homicide, more than 30 percent of the inmates sentenced to life without parole in eight states were convicted of something other than homicide, the report found. In Washington State, for example, two-thirds of the people sentenced to life without parole since 1994 received that sentence because of the state's three-strikes law.

In at least 37 states, life without parole is available for convictions like burglary, robbery and carjacking, according to the report. Florida leads the country in life without parole prisoners, with almost 8,000.

“The idea of whole-life prison sentences easily won approval in a period of growing skepticism about the value of rehabilitation,” says the report. “Instead, punishment and incapacitation became identified as the primary goals of imprisonment and many abandoned the idea of reforming offenders.”

'Aging out' of crime

Data show that crime has steadily declined since the 1980s, with violent crime rates now at their lowest point in decades. But as time passes, that crackdown is having knock-on effects, such as overcrowded prisons straining state budgets. Life without parole sentences are particularly relevant to budgets, given that prisons spend two to three times more to incarcerate an elderly prisoner – on average about $70,000 a year – than a younger one, according to Marie Gottschalk, a political scientist at the University of Pennsylvania.

Meanwhile, a growing body of research suggests many people “age out” of criminal behavior. A 2004 report by the Sentencing Project notes that criminals released after receiving life sentences with parole were rearrested at much lower rates than the overall prison population – 21 percent versus 68 percent.

Nearly 2,500 of the 50,000 inmates sentenced to life without parole were convicted of crimes that occurred before they turned 18, the Sentencing Project found.

“People will debate if people are deserving of long term sentences and if societies should punish, and that’s a legitimate debate to have,” says Marc Mauer, director of the Sentencing Project. “[But] we do know there are many people who have changed substantially after a couple decades of incarceration and don’t present nearly the public safety risk they did at the time of their crime.”

Hartman agrees, saying he would barely be able to recognize his 19-year-old self.

“I can’t even imagine the person I was when I was 19, it’s almost like another human being. And I think that’s probably true for every human being,” adds Hartman.

A humane alternative?

For Mr. Tsarnaev, the question of life without parole is different. If he were sentenced to spend the rest of his life in prison, it would be to spare him from execution.

But Hartman, for one, takes issue with the argument that life without parole is more humane than the death penalty.

“You’re basically sentenced to a long, slow death,” he says. “It’s like you were killed a long time ago, and now you’re sort of waiting around for it to come to an end.”

It is an issue that has come up in the Tsarnaev trial in Boston. In trying to spare Tsarnaev’s life, his defense lawyers have argued that his life in the super maximum security prison in Florence, Colo., will be punishment enough.

“There is no privacy. A camera will be trained on him 24 hours a day," defense attorney David Bruck said. "There will be no autobiography, no execution date to bring him back into relevance."

“This is where the government keeps other terrorists who used to be famous but aren’t anymore,” he added.

Compared with executing a criminal, life without parole can appear more humane. But that comparison is unhelpful, suggests Ms. Vannier of Oxford.

“It’s this bizarre situation where you’ve got two extreme forms of sentences, and one attracts attention, [while] the other basically attracts none,” she says.

Death penalty abolitionists have supported the expansion of life without parole as more states have used it as an alternative to the death penalty.

A 2010 poll in California found that support for capital punishment fell from about 70 percent to 41 percent when respondents were presented with life without parole as an alternative. A Boston-area poll taken in the first weeks of the Tsarnaev trial found that the majority of respondents favored life without parole over the death penalty.

“Life without parole will always come second as long as the death penalty is on the books,” says Vannier.

In some ways, that makes life without parole worse than a death sentence, Hartman says, because criminals sentenced to death are more a focus for activists and lawyers.

“People sentenced to death exist in a separate universe in many ways,” says Hartman. “They have more legal options coming, they have more attention from abolitionist groups and legal support groups.”

In 2012, death row inmates in California state prisons took the radical step of opposing the commutation of their sentences precisely because they would have been transferred to a life without parole sentence. In 2013, the European Court of Human Rights ruled that life without parole was “inhuman and degrading” and violated the European Convention of Human Rights because prisoners must have some prospect of release and incentive to rehabilitate.

Seeking solutions

For most life without parole opponents, the solution is simple: replace it with life with parole. Mr. Mauer has suggested a 20-year cap on federal prison terms with an option for parole boards or judges to add more time if necessary to protect the public.

But such a solution isn’t so easy. Victims’ rights groups argue that parole hearings amount to a form of recurring torture. Jennifer Bishop-Jenkins, whose sister was murdered while pregnant, says that parole hearings represent “a lifelong nightmare” for victims’ families.

“Whatever the outcome, at some point for us the process has to end,” adds Ms. Bishop-Jenkins, who is also president of the National Organization of Victims of Juvenile Murders. “Could you at least give us that? A point at least where we don’t have to go to court and look at this offender?”

“That’s what victims’ families need. At some point we need some legal finality,” she adds.

The US is beginning to at least consider some of these questions. There is bipartisan support in Congress for reduced mandatory minimum sentences, and a decline in death sentences points to a broader reconsideration of the punishment. The American Pharmacists Association, for example, recently voted to oppose participation in executions.

The question, Hartman says, is whether that will simply increase the number of people in prison for life with no hope of ever getting out.

“The problem is, I imagine there’ll be 100,000, 150,000 people sentenced to a long, slow death in prison until people finally step back and think, ‘Is this the right thing to do? Does this make sense?’ ”